1. Technical Field of the Invention
The present invention relates to an evaluation device for evaluating mist generation in a light chamber of a vehicle lighting device.
2. Related Art
In general, a vehicle lighting device includes a light chamber composed of a front lens and a lamp body. In many cases, at a rear portion of the lamp body, there is provided a vent hole for communicating the light chamber with an outer space of the lighting device. Due to the above structure, even when the lighting device is repeatedly turned on and off, the pressure in the lighting chamber is prevented from changing. Therefore, mist (as caused by moisture) is seldom created in the light chamber.
In the vehicle lighting device composed as described above, unless consideration is sufficiently given to the structure and arrangement of a vent hole, moisture gets into the light chamber from the outer space of the lighting device via the vent hole. When moisture gets into the light chamber, dew condensation is caused on the inner face of the lens, which results in the generation of mist.
Heretofore, it has been impossible to accurately evaluate the above generation of mist by using a bench test. Therefore, the evaluation of mist generation is made in such a manner that the lighting device is incorporated into a true vehicle and the generation of mist is evaluated while the vehicle is running.